(a) Field of the Invention
This invention relates a guidance system for boring equipment and more particularly, but not by way of limitation, to a system for keeping a tunnel boring machine continuously on a plan line by providing a boring machine operator with a graphic display of past, present and projected positions of the boring machine. The new guidance system, while used primarily for tunneling, can also be used equally well in shaft sinking, mining and other boring applications.
(b) Discussion of Prior Art
In U.S. Pat. Nos. 3,707,330 to Pine and 3,484,136 to Colson, a method and apparatus for guiding a tunneling machine with a light beam and a pair of targets is disclosed. The targets are mounted on the equipment and designed to return to an operative position when the machine rolls about its longitudinal axis. U.S. Pat. No. 3,321,248 to Williamson et al. also describes the use of a pair of targets on a tunneling machine with impingement using a laser beam.
U.S. Pat. No. 3,517,966 to Montacie describes a guidance system for a boring machine wherein the laser source is used in conjunction with an optical system mounted on the machine. U.S. Pat. Nos. 3,498,673 to Ledray et al. and 3,482,103 to Martinsen describe the use of a mirror reflector and photocells with a light source in guiding a tunneling machine. Further, U.S. Pat. Nos. 4,656,743 to Thiemann et al., 4,273,468 to Cyfka and 3,560,753 to Beug et al., describe different types of system dealing with the position or displacement of a boring machine along with a tunnelling shield.
None of the above mentioned prior art patents specifically disclose the unique features, advantages and method steps of the subject system for keeping a tunnel boring machine continuously on a plan line.